Production of azo dyes



United States Patent 3,297,679 PRODUCTION 0F AZO DYES Dieter Leuchs, Ludwigshafen (Rhine), Germany, assignor to Badische Anilin- & Soda-Fabrilr Alrtiengesellschaft, Ludwigshafen (Rhine), Germany No Drawing. Filed Aug. 15, 1963, Ser. No. 302,445 7 Claims. (Cl. 260206) This invention relates to a new process for the production of azo compounds from Z-hydrazones of 1,2,3-trioxo compounds.

Numerous azo dyes having a phenolic coupling component are known. They are usually obtained by coupling a diazo compound with a phenol. Only a few azo dyes have been described however which contain a phenol substituted on the benzene ring. With a few exceptions, such as o-cresol, m-cresol or o-phenylphenol, substituted phenols which are capable of coupling cannot be prepared or can only be prepared with .great difficulty. Therefore azo dyes suitable for the production of certain substituted aminophenols by reductive cleavage of azo dyes containing phenol coupling components have hitherto not been available in practice.

It is the object of the present invention to provide a process by means of which azo compounds may readily be prepared which contain a phenol component bearing alkyl, aryl or aralkyl radicals as substituents.

This object is achieved in accordance with this invention by preparing azo compounds having the general for mula:

in which A denotes the radical of a diazotizable amino compound and R R and R may be identical or different and denote hydrogen atoms, alkyl radicals, preferably alkyl radicals having one to four carbon atoms, aryl radicals, preferably phenyl radicals, or aralkyl radicals, by condensation of a hydrazone having the general formula:

R1 i=0 A-N'HN=C GH=O (11 with a ketone having the general formula:

II R CHiGoHzR (III) in which A, R R and R have the meanings given above, in the presence of a basic condensing agent.

A particular object of the invention is the production of compounds having the Formula I in which R R and R denote methyl radicals andA preferably denotes the radical of a diazotizable amine of the benzene series.

These compounds are suitable for a simple synthesis, proceeding particularly uniformly, of trimethylhydroquinone which is an intermediate for the production of tocopherol. This is explained in greater detail below.

Hydrazones having the Formula II which are used as initial materials for the production of the azo compounds have been described in the literature. They are obtained for example by coupling aliphatic or araliphatic 1,3-dihydroxy compounds or their functional derivatives, such as enol ethers, enamines or acetalenol ethers, with diazonium compounds (see L. Claisen, Ber., 36, 3668 (1903); L. Claisen, Ber., 21, 1697-1705 (1888); German patent specification No. 947,468). Starting compounds which have not yet been described may be prepared analogously ice to the known compounds. The radical A in Formula II may be the radical of any diazotizable aromatic-isocyclic or aromatic-heterocyclic amine.

The 2-phenyl hydrazones of propanone-(2)-dial-(1,3), of butanedione-(2,3)-al and of 3-phenylpropanedione- (2,3)-al which may bear alkyl radicals having one to four carbon atoms, alkoxy radicals having one to four carbon atoms, phenylazo groups, sulfonic acid groups, nitro groups or halogen atoms as substituents in the phenyl radical may however be used with particular advantage as initial materials for the new process.

Examples of ketones having the Formula III are acetone, butanone-(Z), pentanone-(Z), pentanone-(b), hexanone-(2), heptanone-(3), heptanone-(4), 2,6-dimethylheptanone-(4), phenylacetone and 1,3-diphenylacetone.

Examples of basic condensing agents for the reaction according to this invention are alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal alcoholates, alkali metal carbonates and tertiary aliphatic amines. They are advantageously used in at least a 0.5-molar amount and preferably in a 1-m0lar amount. Larger amounts of condensing agent may be used but there is no further acceleration of the reaction in consequence.

The condensation yielding the azo compounds is carried out in water and/or organic solvents, such as aliphatic alcohols, dialkylformamides, or in an excess of the ketone component having the Formula III, depending on the solubility characteristics of the reactants. The condensation will proceed within a wide temperature range, for example between 0 and 150 C. Since at 0, however, appreciable amounts of byproducts and decomposition products begin to form, the condensation is advantageously carried out in the range from 10 to 50 C.

The azo compounds formed according to this invention may be deposited and isolated by conventional methods by neutralization of the basic condensing agent with acids and if necessary by dilution of the reaction mixture with water. Products containing sulfonic acid groups can usually be isolated merely by salting out from the reaction mixture.

The azo compounds obtainable according to the process may be used as inter-mediates for the production of paminophenols and their secondary products, such as quinones and hydroquinones. In particular, as already mentioned, trimethyl-hydroquinone may be readily prepared from an azo compound having the Formula I in which R R and R denote methyl groups.

Prior art methods for the production of trimethylhydroquinone usually start from 1,2,4-trimethylbenzene (pseudocumene) present in coal tar and which already contains the methyl groups in the correct positions. The diculties of this method of preparation consist in introducing into each of the 3 and 6-positions a hydroxyl group or a substituent convertible into a hydroxyl group. Since the 5-position in 1,2,4-trimethylbenzene is the first to be occupied by freshly introduced substituents, this position must first be blocked by a substituent which can later be eliminated. For this purpose it has hitherto been usual to introduce a sulfonic acid group (Pongratz, Zirm, Monatsh, 83 (1952), 13) or a bromine atom (Hui, I. Vitaminology, 1 (1954), 8).

It [has also been proposed to convert 2,3,5-trimethylphenol into the hydroquinone by coupling with diazonium salts, reductive cleavage, oxidation to the quinone and reduction to the hydroquinone (Smith et al., J. Org. Chem., 4 (1939), 318). According to another proposal, the same phenol is converted into the trimethylhydroquinone by nitrosation, hydrolysis of the nitrosophenol and reduction of the quinone (Boscott, Chem. and Ind, 1955, 201). The 2,3,5-trimethylphenol required for these methods cannot however be prepared from 1,2,4-trimethylbenzene direct and free from isomers because of the preferential substitution of the -position of 1,2,4-trimethylbenzene.

The said methods consequently necessitate a number of steps and therefore give low total yields.

amines, used in at least 0.5-molar amounts, are for example suitable as condensing agents.

The hydroxyazo compound thus prepared is then reductively split to the aminophenol, for example in mineral In contrast we have found that trimethylhydroquinone 5 acid solution with zinc or stannous salts or in neutral or can be prepared advantageously and in high yields by weakly alkaline solution with sodium dithionite (2). converting an azo compound having the formula: Acid reduction is most advantageous industrially; it is expedient to use sulfuric acid for the purpose. The use of (3H1 hydrochloric acid would give, in the subsequent oxidation of the aminophenol (which can be carried out in the same A N=N reaction medium without isolation of the intermediate product), chlorotrimethylbenzoquinone by addition of H3 hydrochloric acid to the trimethylquinone formed, instead A by 2 process i g to thlslmventlon 3 tnmethiL ric sulfate rather than with ferric Zhloride which is con t t t 3583: gggi g g g ifi igz ggi gz a Ion o e ventionally used. The tnmethylbenzoqumone formed is The course of the reaction may be represented by the t gg fii g the reaction mlxture for example by Steam f t'o l Onowmg equa 1 ns Reduction (4) of the trimethylbenzoqumone to tn- (1) on 0 methylhydroquinone may be effected for example in aqueous suspension with sulfurous acid, alkali metal sulfites, 9 II B NaOH alkali metal bisulfites or sodium dithionite, if desired with =0 the addition of an inert organic solvent which is not mis- CH=O mo cible with water, such as benzene, chlorobenzene, chloro- Cm form or methylene chloride. The aqueous suspension of CH CH trimethylbenzoquinone may be the steam distillate from a 3 the preceding stage. The trimethylhydroquinone ob- 903 tamed is very pure.

N N Q The invention 15 further illustrated by the following CH3 Examples in which parts are by weight unless otherwise (2) CH stated. Parts by weight bear the same relation to parts 3 3 by volume as the kilogram to the liter (S.T.P.). The

4H percentages are also by weight.

Example 1 176 parts of mesoxaldialdehyde monophenylhydrazone (IIHE E is stirred into 1000 parts by volume of ethyl alcohol and 9 then 95 parts of diethyl ketone and 440 parts of 10% O3s N211 0H caustic soda solution are added. The reaction mixture is boiled for three hours under reflux and then cooled to room temperature. It is then neutralized with 10% (3) b a h hydrochloric acid and the deposited dye is filtered off by suction. 185 parts of the dye having the formula: 1nNorr o: CH 3 l 1 H3 (4 cm C113 flir O: '0

0 1s obta1ned.

E Ha If the reaction is carried out at room temperature, stirring must be continued for twelve hours to complete the The hydrazone compound is condensed in aqueous Converslbnsolution with diethyl ketone in the presence of a basic If the ethyl alcohol 111 the abQVe example be p e y condensing agent to a compound containing a 2,3,5-trimethyl alcohol and the Caustle Soda y an equivalent methyl-4-hydroxyazo radical (1). Alkali metal hydroxamount of caustic potash, the dye is obtained in almost the ides, alkaline earth metal hydroxides, alkali metal carsame yield. bonates, alkali metal alcoholates and tertiary aliphatic The following dyes are obtained in the same way:

lilqx. Phonyl hydrazone Ketone i End product NHN=C\ Acetone N:N--on CH 3. Same as tbove Methyl ethyl N=NOII ketone.

Example 14 is obtained.

The hydroxyazo dye thus obtained is converted into trirnethylhydroquinone as follows:

The dye is stirred with 2000 parts of 20% sulfuric acid, 20

1 part of mercuric chloride is added and reduction is effected by introducing 160 parts of zinc dust in portions.

The temperature of the reaction mixture thereby rises to the boiling point. After the last portion of zinc has been added, the whole is boiled for about an hour under reflux while stirring until a clear solution is obtained. The solution is then transferred to a steam distillation apparatus, a solution of 400 parts of ferric sulfate is added and the trimethylbenzoquinone formed is distilled off with steam. Without isolating the oily quinone, half the volume of benzene is added to the distillate and the quinone is reduced by scattering 300 parts of sodium dithionite therein while stirring vigorously. The trimethylhydroquinone which has crystallized out is filtered off by suction, washed with ice-water and dried at 40 C. under subatmospheric pressure. 92 parts of trimethylhydroquinone having a melting point of 172 C. is obtained. The yield, with reference to the azo dye used, is 65% of the theory. The melting point rises to 174 C. after a single recrystallization from hot water.

Using the same process as described in paragraph 1 of this example, the following p-hydroxyazo compounds are obtained from the initial compounds specified:

Example No. Phenyl hydrazone Ketone End product C H O 15 NaO=S-NHN=C\ Acetone Naois- N=N -Ol 16 Same as above. Methyl ethylketone- N 21038-6 N=N O H 17. Same as above Dicthyl ketoue N aO3SN:N Oll 18 Same as above Mcthylbutyl ketone. moss- N=N O1I (33 17 3 one L 19. Same as above Dipropyl ketone N aO;S- N=N- -OII (lzlla 20 Same as above Dibenzyl kctone NaO3S -N=N- -OII l i C [is /C=O 21- NaOgS-NIIN=C\ Acetone NaOzS- N=N -0II $111 22 Same as above Methyl ethyl ketone--. NaO3S'N=N -orr C II:

l 23 Same as above. Methyl bcnzyl ketone. NaO;S- -N=N- @011 Example N 0. Phenyl hydrazone Ketone End product :0 I 24 Na0aSNH-N==O Acetone NaO3SN=N0H CEO on, I l 25 Same as above Dlethylketone NaO SN=NQ 0H Instead of caustic soda solution as the condensing agent, there may be used caustic potash solution, sodium carbonate or potassium carbonate or, when working in an anhydrous medium, sodium methoxide or sodium ethoxide with the same result.

I claim:

1. A process for the production of azo compounds of the formula where R represents a member selected from the class consisting of hydrogen, halogen, alkyl of 1 to 4 carbon atoms, alkoxy of 1 to 4 carbon atoms, nitro, sulfonic acid and phenylazo, and R R and R are members selected from the class consisting of hydrogen, alkyl of l to 4 carbon atoms and phenyl, which process comprises: condensing a hydrazone of the formula C H=O with a ketone of the formula where R R R and R have the same meanings as above, in an aqueous or organic solution at a temperature from about 0 to 150 C. in the presence of a basic condensing agent selected from the class consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal alcohoaltes, alkali metal carbonates and tertiary aliphatic amines.

2. A process as claimed in claim 1 wherein R R and R each represent methyl.

3. A process as claimed in claim 1 wherein the temperature is about to 100 C.

4. A process as claimed in claim 2 wherein the temperature is about 10 to 100 C.

5. A process as claimed in claim 4 wherein the ketone is diethyl ketone,

6. A process for the production of the azo compound of the formula CH OH;

7. A process for the production of the azo compound of the formula which comprises: condensing at about 10 to C. the hydrazone of the formula with diethyl ketone in an aqueous or organic s-olutionin the presence of a basic condensing agent selected from the class consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal alcoholates, alkali metal carbonates and tertiary aliphatic amines.

No references cited.

CHARLES B. PARKER, Primary Examiner. JOSEPH P. BRUST, Examiner.

F. D. HIGEL, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,297,679 January 10, 1967 Dieter Leuchs It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the heading to the printed specification, after line 6, insert Claims priority, application Germany, August 23, 1962 column 3, under the heading Phenyl hydrazone,

last line, for "tbove" read above column 9, line 59, for "alcohoaltes" read alcoholates Signed and sealed this 17th day of October 1967.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Commissioner of Patents Attesting Officer 

1. A PROCESS THE PRODUCTION OF AZO COMPOUNDS OF THE FORMULA 